Wait for next chunk of data


I am trying to write a lua fetch function to be able to redirect POST requests according to a value in the POST data.

The problem I am incurring is that I cannot find a way to make HAProxy wait for all the POST data to arrive - if for some reason this arrives in two chunks, haproxy will only make its decision using just the first chunk.

Here are my haproxy.cfg and mylua.lua. The current configuration tries to match the string “TWO” in the post data and if so the request should get passed to backend be2

lua-load ./mylua.lua

mode http
timeout connect 3s
timeout client 8s
timeout server 3s

frontend fe
mode http
acl acl_be2 lua.check_post -m str “TWO”

use_backend be2 if acl_be2
default_backend be1

backend be1
mode http
server s

backend be2
mode http
server s

`function check_post(txn)
local all_data=txn.req:dup()

if string.match(all_data, “TWO”) then
return "TWO"
return "ONE"


core.register_fetches(“check_post”, check_post)

The problem occurs only when the request gets chunked. For example the request below gets delivered to backend be1 instead of be2:
sh-4.2# (echo 'POST / HTTP/1.1 User-Agent: curl/7.26.0 Host: Accept: */* Content-Length: 11 Content-Type: application/x-www-form-urlencoded '; sleep 2; echo '1234TWO1234'; ) | nc 127.1 8001

However if I remove the “sleep 2”, the request is not chunked and request goes to backend be2 as expected.

My question is how can I perform such decisions by matching content on the POST data and be sure that this will always work?


Hi darkolee -

You may want to look into the http-buffer-request keyword, though I’m not sure it’ll solve the chunked part of the problem (but it may help). You may also look into tcp-request inspect-delay .

Hope that helps!

  • Andrew